Chemistry question (could be biology, too)

[JohnCU]

Red blood cells are placed into pure water. Which of the following statements is true?

A. Water molecules flow out of the red blood cells, causing them to collapse.
B. Water flows into the red blood cells, causing them to swell and burst.
C. The osmotic pressure inside the cell decreases, causing the cells to burst.
D. The osmotic pressure inside the cell equals the osmotic pressure outside.

I picked B, but I don't understand osmosis very well. 🙁

 

[theNEOone]

you picked right.



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[BigPoppa]

Osmosis:

Theres no water inside the red blood cell, thus it wants to equalize the osmotic pressure. Water enters the cell, the cell bursts.

 

[h8red]

Originally posted by: theNEOone
you picked right.

yep

 

[theNEOone]

Originally posted by: BigPoppa
Osmosis:

Theres no water inside the red blood cell, thus it wants to equalize the osmotic pressure. Water enters the cell, the cell bursts.

ok not to nitpick, but there is plenty of water in the RBC. the problem is with the collective concentrations of diluted molecules (which are impermeable to the cell membrane) inside the RBC. i'll call this concentration [M].

if the concentration of [M] is only slightly higher inside the cell than outside, then only a little bit of water is needed to equalize concentrations. however, [M] is CONSIDERABLY higher inside the cell, than outside. as a result, there will be a net influx of water molecules, causing the osmotic pressure within the cell to become more than the cell membrane can withstand.



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